Blast injury research models.

Abstract

Blast injuries are an increasing problem in both military and civilian practice. Primary blast injury to the lungs (blast lung) is found in a clinically significant proportion of casualties from explosions even in an open environment, and in a high proportion of severely injured casualties following explosions in confined spaces. Blast casualties also commonly suffer secondary and tertiary blast injuries resulting in significant blood loss. The presence of hypoxaemia owing to blast lung complicates the process of fluid resuscitation. Consequently, prolonged hypotensive resuscitation was found to be incompatible with survival after combined blast lung and haemorrhage. This article describes studies addressing new forward resuscitation strategies involving a hybrid blood pressure profile (initially hypotensive followed later by normotensive resuscitation) and the use of supplemental oxygen to increase survival and reduce physiological deterioration during prolonged resuscitation. Surprisingly, hypertonic saline dextran was found to be inferior to normal saline after combined blast injury and haemorrhage. New strategies have therefore been developed to address the needs of blast-injured casualties and are likely to be particularly useful under circumstances of enforced delayed evacuation to surgical care.

(a) Kaplan–Meier survival plot, (b) mean survival times (95% CI) for four groups of animals subjected to either sham blast (S) or blast (B), haemorrhagic shock and resuscitation to either a normotensive (Normot) or hypotensive (Hypot) arterial blood pressure. No 95% CI is shown for S Normot group as all survived to the end of the observation period, 480 min after the start of resuscitation.

(a) Arterial base excess (ABE) and (b) oxygen extraction ratio (OER) in four groups of animals subjected to either sham blast (sham) or blast (blast), haemorrhagic shock and resuscitation. The first dotted line represents the onset of resuscitation (hypotensive in all groups). The second dotted line indicates the onset of normotensive resuscitation in NH groups and continued hypotensive resuscitation in the Hypot groups. For further explanation of figure see legend to .

Systemic arterial blood pressure response to infusion of hypertonic saline dextran (HSD) in four individual animals. All animals had received a controlled haemorrhage followed by a grade IV liver injury. Preceding the haemorrhage animals were either subject to blast injury or no blast injury as follows: (a) no blast injury, good response to HSD; (b) blast injury, good response to HSD; (c) blast injury, poor response to HSD, target blood pressure was not attained before animal died; (d)(i) blast injury, initial good response to HSD and attainment of target blood pressure followed approximately 15 min later by (d)(ii) catastrophic collapse and death. Blocks labelled HSD indicate periods of HSD infusion.

(a) Arterial oxygen tension (PaO2) and (b) saturation (SaO2) in two groups of animals subjected to blast injury, haemorrhage and hypotensive resuscitation. Time indicates time from the onset of resuscitation which was initiated at the first dotted line. Second dotted line (30 min after the onset of resuscitation) represents the divergence of treatment groups with supplemental inspired oxygen being introduced into the blast O2 group while the blast Hypot group continue to breathe air. First two values represent baseline, followed by post blast, pre and post haemorrhage and then the onset of resuscitation. Open symbols indicate 66% of animals surviving. No data plotted when proportion surviving fell to 50% or below. Mean values ± s.e.m.

Kaplan–Meier survival plot for two groups of animals subjected to blast injury, haemorrhage and hypotensive resuscitation. The Blast O2 group was given supplemental oxygen to elevate SaO2 to 95% starting 30 min after the onset of resuscitation, while blast Hypot continued to breathe air throughout.

(a) Arterial base excess (ABE) and (b) oxygen extraction ratio (OER) in two groups of animals subjected to blast injury, haemorrhage and hypotensive resuscitation. For further explanation see legend to .